Along with miniaturization of a semiconductor pattern, a slight difference in shape affects operating characteristics of devices, and needs for management of shapes are increased. Accordingly, high sensitivity and high accuracy are required more than before in a scanning electron microscope (SEM) used for inspecting and measuring semiconductors. In the SEM, when a sample is irradiated with an electron beam, secondary electrons emitted from the sample is detected to observe a surface shape. At this time, the secondary electrons to be detected have low energy and are easily affected by charging of the sample. Effects of charging become obvious by the use of low-dielectric constant materials such as low-k, and there is a case where it is difficult to capture a signal in a region necessary to be managed (ROI: Region Of Interest). Also in normal detection of secondary electrons, there exists a case where observation itself becomes difficult due to miniaturization and high aspect ratio in holes and trenches in recent years.
In such case, to relatively emphasize information of an observation position by discriminating electrons to be detected according to energy or angles of electrons can be a solution.
In Patent Literature 1, there is disclosed, in an electron microscope including an energy filter, a method of finding an applied voltage of an energy filter in which luminance variation is increased by creating a graph indicating the applied voltage of the energy filter and the luminance in a beam irradiation unit. Also, in Patent Literature 2, there is disclosed, in a scanning electron microscope including an energy filter, a method of calculating an optimum filter voltage from a gradation ratio of images by selecting two areas and acquiring images in the areas where the filter voltage is changed. In Patent Literature 3, there is disclosed a method of determining a filter voltage in which the maximum contrast is obtained by detecting signal intensities at the time of changing an energy filter voltage and calculating a contrast from signal intensities at two points.